Corrosion inhibitors are commonly found in cleaning and stripping compositions used in the semiconductor industries where various metals such as aluminum, aluminum alloys, titanium, titanium alloys, titanium/tungsten, tungsten, copper, etc are utilized.
The different functional classifications by which corrosion inhibitor compounds can be categorized are as follows:
1. Chelating agents
2. Reducing agents
3. Oxygen scavengers
4. Film forming agents
5. Oxidizing agents which form a protective film, typically of metal oxide.
None of the corrosion inhibitor types are effective for all mechanisms of corrosion or for all metal or metal alloys. Oxygen scavengers are not particularly effective at eliminating oxygen induced corrosion of iron or its alloys in the presence of an aqueous solution of high ionic character. Neither prior art corrosion inhibitors used in the semi-conductor industry that are chelating agents or oxygen scavengers are effective in preventing corrosion of iron or carbon steel in the presence of water, oxygen or high ionic activity aqueous or semi-aqueous solutions.
U.S. Pat. No. 3,996,147 to Settineri et al discloses the use of sulfonium corrosion inhibitors which inhibit corrosion of metal surfaces, particularly ferrous and cuprous metal surfaces in aqueous acid solutions alone or in combination with other chelating agents such as an aminocarboxylic acid, for example, ethylene diaminetetraacetic acid (EDTA).
U.S. Pat. No. 5,334,332 to Lee et al, which is herein incorporated by reference discloses chelating agents and solvent systems which can be used with the inhibitors of the present invention. The reference does not disclose a film forming polymeric chelating agent.
U.S. Pat. Nos. 5,707,947 and 5,753,601, which are herein incorporated by reference, disclose phenol derivatives that adsorb onto or absorb into the surface of neutral (zero valent) metals and/or chelation of their anions with the oxidized cationic metal surface which reduces the dissolution rate of the oxidized surface.